Treatment chair

Abstract

Improvements in a treatment chair whose backrest frame is designed to be tiltable with respect to the seat frame of the chair by use of a roller rotating within a guide groove are disclosed. In the disclosed embodiments all utilize an arc segment portion groove. As a result, the top portion of the backrest frame holds substantially the same peripheral speed throughout travels with raising and lowering of the backrest frame and the patient resting against the backrest frame is thereby free from any uncomfortable feeling due to preceptible changes in peripheral speed during the rise and fall movement of the frame.

I claim: 
     
       1. An improved chair of the type comprising (a) a seat frame, (b) a roller supported at the end of said seat frame, (c) a backrest frame, (d) a guide fixed in location with respect to said backrest frame adapted to rotatably fit said roller therein and (e) a driving mechanism connected to said seat frame and to said backrest frame for causing a point on the lower end of said backrest frame to arcuately travel along a path lying below the position in which said frame rotates in contact with said roller; wherein the improvement comprises said guide groove comprising an arcuate portion having a center curvature on the front side of said backrest frame facing said seat frame and located so as to result in the peripheral speed of the upper portion of said backrest frame being maintained at a constant value during the raising and lowering of said backrest frame.   
     
     
       2. A treatment chair according to claim 1, wherein said guide groove arcuate portion is substantially in the shape of an arc segment of a true circle. 
     
     
       3. A treatment chair according to claim 1, wherein said guide groove is substantially in the shape of an arc segment of an oval. 
     
     
       4. A treatment chair according to claim 1, wherein the upper and lower portions of said guide groove are substantially in the shape of a circular arc segment and wherein said arc segments are connected by a straight line.